Spectrophotometer

ABSTRACT

Observation light can be applied to a position for measurement without providing large space in a spectrophotometer, and the position for measurement can be easily known. A slit is disposed at a position optically conjugate with the position for measurement in the spectrophotometer. Light from an object to be measured passes through the slit, travels along a measurement optical path, and is subject to wavelength dispersion by a wavelength dispersing element. An observation light source is retracted outside the measurement optical path at the time of measuring a spectral spectrum. At the time of observing the position for measurement, the observation light source is inserted into the measurement optical path, and emits observation light toward the slit. Alternatively, light from an object to be measured passes through the slit, and is diffracted by a grating. The observation light source is disposed on an optical path of zeroth light. The observation light source emits observation light toward the grating at the time of observing the position for measurement.

RELATED APPLICATIONS

This is a U.S. National Phase Application under 35 USC 371 ofInternational Application PCT/JP2018/016602 filed on Apr. 24, 2018.

This application claims the priority of Japanese application no.2017-109177 filed Jun. 1, 2017, the entire content of which is herebyincorporated by reference.

TECHNICAL FIELD

The present invention relates to a spectrophotometer.

BACKGROUND ART

In a case where a spectrophotometer for measuring a spectral spectrumhas a minute range for measurement, a spectral spectrum to be measuredmay greatly change from a spectral spectrum of light at an intendedposition even when a position for measurement is only slightly deviatedfrom the intended position. For this reason, in the case where aspectrophotometer has a minute range for measurement, it is desired thatthe position for measurement can be observed before measurement and theposition for measurement can be moved to the intended position beforethe measurement. Patent Literature 1 discloses an example of a techniquethat enables such a thing in a spectroscope.

In the technique disclosed in Patent Literature 1, a shutter is closedwhen observation light is injected. An LED applies observation lighttoward the shutter. The shutter reflects the applied observation lighttoward an objective lens. The objective lens images the reflected lighton the surface of an object to be measured. A measurement site isidentified from the position of the light imaged on the surface of theobject to be measured. When measurement is performed, the shutter isopened, and light that has passed through a slit mirror is guided to alight receiving unit (paragraphs 0027 to 0031).

CITATION LIST Patent Literature

Patent Literature 1: JP 2009-288150 A

SUMMARY OF INVENTION Technical Problem

In traditional techniques represented by the technique disclosed inPatent Literature 1, large space needs to be provided in aspectrophotometer for accommodating a mechanism for applying observationlight at a measurement position in the spectrophotometer. For example,in the technique disclosed in Patent Literature 1, large space needs tobe provided in a spectroscope for accommodating, for example, a slitmirror in the spectroscope.

The invention described below aims to solve the problem. A problem to besolved by the invention described below is to enable application ofobservation light to a position for measurement without providing largespace in a spectrophotometer, and to enable the position for measurementto be easily known.

Solution to Problem

The invention described below relates to a spectrophotometer.

(1) In the first invention described below, light to be measured from aposition for measurement is imaged by a light-receiving optical system.This generates imaged light to be measured.

The imaged light to be measured passes through a slit disposed at aposition conjugate with the position for measurement. This generateslight to be measured, which travels along a measurement optical path.

The light to be measured, which travels along a measurement opticalpath, is subject to wavelength dispersion by a wavelength dispersingelement. This generates light that has been subject to wavelengthdispersion.

A sensor receives the light that has been subject to wavelengthdispersion, and outputs a signal representing a spectral spectrum.

An insertion/extraction mechanism inserts an observation light sourceinto a measurement optical path at the time of observing a position formeasurement, and retracts the observation light source outside themeasurement optical path at the time of measuring the spectral spectrum.

The observation light source emits observation light toward the slit atthe time of observing the position for measurement.

(2) In the second invention described below, light to be measured from aposition for measurement is imaged by a light-receiving optical system.This generates imaged light to be measured.

The imaged light to be measured passes through a slit. This generateslight to be measured, which travels along a measurement optical path.

The light to be measured, which travels along the measurement opticalpath, is diffracted by a grating. This generates diffracted light. Thelight to be measured, which travels along the measurement optical path,is reflected by the grating. This generates zeroth light.

A sensor receives the diffracted light, and outputs a signalrepresenting a spectral spectrum.

An observation light source is disposed on an optical path of the zerothlight, and emits observation light toward the grating at the time ofobserving the position for measurement.

Advantageous Effects of Invention

According to the invention described below, observation light can beapplied to a position for measurement without providing large space in aspectrophotometer, and the position for measurement can be easily known.

The following detailed description and accompanying drawings will makethe object, feature, aspect, and advantage of the invention clearer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating a spectrophotometer of afirst embodiment.

FIG. 2 is a schematic diagram illustrating a cross section of aspectroscope provided in the spectrophotometer of the first embodiment.

FIG. 3 is a schematic diagram illustrating a partial cross section ofthe spectroscope provided in the spectrophotometer of the firstembodiment and a driving mechanism of an observation light source.

FIG. 4 is a schematic diagram illustrating an observation light sourcewith which the observation light source provided in thespectrophotometer of the first embodiment can be replaced.

FIG. 5 is a schematic diagram illustrating a spectrophotometer of asecond embodiment.

FIG. 6 is a perspective view illustrating placement of a grating in thespectrophotometer of the second embodiment.

FIG. 7 is a perspective view illustrating placement of the gratingcompared to the placement of the grating in the spectrophotometer of thesecond embodiment.

DESCRIPTION OF EMBODIMENTS 1. First Embodiment

1.1 Spectrophotometer

FIG. 1 is a schematic diagram illustrating a spectrophotometer of afirst embodiment. FIG. 2 is a schematic diagram illustrating a crosssection of a spectroscope provided in the spectrophotometer of the firstembodiment. FIG. 3 is a schematic diagram illustrating a partial crosssection of the spectroscope provided in the spectrophotometer of thefirst embodiment and a driving mechanism of an observation light source.

FIG. 2 illustrates a cross section at the position of an A-A cuttingplane line in FIG. 3. FIG. 3 illustrates a partial cross section at aB-B cutting plane line in FIG. 2.

A spectrophotometer 1000 in FIG. 1 includes an illumination opticalsystem 1020, a light-receiving optical system 1021, a spectroscope 1022,a controller 1023, and an operation unit 1024. The spectrophotometer1000 may include a component other than these components.

The spectrophotometer 1000 has d/8 geometry, and is used for an objectcolor. The illumination optical system 1020 in the spectrophotometer1000 illuminates a sample with diffused light. The light-receivingoptical system 1021 receives light to be measured, and guides the lightto the spectroscope 1022. The light to be measured is emitted from thesample in a direction at 8° to the normal direction of the surface ofthe sample. The spectroscope 1022 measures the spectral spectrum of thelight to be measured, which has been guided by the light-receivingoptical system 1021.

The illumination optical system 1020 includes an illumination lightsource 1040 and an integrating sphere 1041. The illumination opticalsystem 1020 may include a component other than these components. Thelight-receiving optical system 1021 includes a light receiving lens1060. The light-receiving optical system 1021 may include a componentother than the light receiving lens 1060. As illustrated in FIGS. 1, 2,and 3, the spectroscope 1022 includes a slit plate 1080, a lens 1081, agrating 1082, a line sensor 1083, an observation light source 1084, andan insertion/extraction mechanism 1085. The spectroscope 1022 mayinclude a component other than these components. A slit 1100 is formedin the slit plate 1080. The slit plate 1080, which is a plate-shapedslit formation, may be replaced with a non-plate-shaped slit formation.The grating 1082 may be replaced with a wavelength dispersing elementother than the grating 1082. For example, the grating 1082 may bereplaced with a prism. The line sensor 1083 including a plurality ofphotoelectric conversion elements arranged in a wavelength dispersiondirection may be replaced with a sensor other than the line sensor 1083.For example, the line sensor 1083 may be replaced with a sensorincluding one photoelectric conversion element. In that case, a scanningmechanism for scanning the sensor in the wavelength dispersion directionis provided. Alternatively, a scanning mechanism that rotationally scansthe wavelength dispersing element in the wavelength dispersion directionis provided.

1.2 Measurement of Spectral Spectrum

The measurement of a spectral spectrum is started in response to thecontroller 1023 detecting an operation for instructing the operationunit 1024 to start the measurement. The trigger for starting themeasurement may be other than the operation for instructing theoperation unit 1024 to start the measurement. For example, the triggerfor starting the measurement may be a signal for giving instruction tostart the measurement. The signal is input from a device connected tothe spectrophotometer 1000 so as to communicate with each other.

At the time of measuring a spectral spectrum, the insertion/extractionmechanism 1085 retracts the observation light source 1084 outside ameasurement optical path 1120 under control of the controller 1023. Theobservation light source 1084 is retracted by a rotation mechanism 1090rotating an arm 1091, to which the observation light source 1084 isattached, around a rotation center 1092.

At the time of measuring the spectral spectrum, the illumination lightsource 1040 emits illumination light for illuminating a sample undercontrol of the controller 1023.

The emitted illumination light enters space 1160 inside the integratingsphere 1041 via an opening 1140 in the side surface of the integratingsphere 1041, and is diffused and multiply reflected by adiffusion/reflection surface 1180 surrounding the space 1160. Thiscauses illumination light to be uniformly diffused.

The illumination light, which has been uniformly diffused, is emittedfrom a measurement opening 1200 in the integrating sphere 1041,illuminates a region facing the measurement opening 1200, and isreflected from the surface of the sample at a position 1220 formeasurement. This generates light 1240 to be measured from the position1220 for measurement.

In order to perform measurement in which regular reflected light isremoved, an openable and closable trap 1260 on the integrating sphere1041 is opened. The regular reflected light is thereby removed.

The generated light 1240 to be measured is imaged on the slit 1100 bythe light receiving lens 1060. This generates imaged light 1280 to bemeasured. The light receiving lens 1060 is movable in the optical axisdirection thereof. The size of a region for measurement can be changedby moving the light receiving lens 1060 in the optical axis directionthereof.

The imaged light 1280 to be measured passes through the slit 1100. Thisgenerates light 1300 to be measured, which travels along the measurementoptical path 1120 between the slit 1100 and the grating 1082.

The light 1300 to be measured, which travels along the measurementoptical path 1120, is guided by the lens 1081, and diffracted by thegrating 1082. This generates diffracted light including minus firstdiffracted light 1320. The light 1300 to be measured, which travelsalong the measurement optical path 1120, is subject to wavelengthdispersion owing to the diffraction. As a result, the minus firstdiffracted light 1320 is light that has been subject to wavelengthdispersion.

The generated minus first diffracted light 1320 is received by the linesensor 1083. The line sensor 1083 may receive diffracted light otherthan the minus first diffracted light 1320.

The line sensor 1083 outputs a signal representing a spectral spectrumcorresponding to the received minus first diffracted light 1320.

1.3 Observation of Position for Measurement

The spectrophotometer 1000 has a function of applying observation lightto the position 1220 for measurement. An operator of thespectrophotometer 1000 can observe the position 1220 for measurement byvisually recognizing a highlight portion, which appears at the time whenobservation light is applied to the position 1220 for measurement,through a finder hole 1340 on the integrating sphere 1041.

At the time of observing the position 1220 for measurement, theinsertion/extraction mechanism 1085 inserts the observation light source1084 into the measurement optical path 1120 under control of thecontroller 1023. The observation light source 1084 is inserted by therotation mechanism 1090 rotating the arm 1091, to which the observationlight source 1084 is attached, around the rotation center 1092. In thestate where the observation light source 1084 is inserted in themeasurement optical path 1120, the light emitting surface of theobservation light source 1084 faces the slit 1100, and the observationlight source 1084 can emit observation light toward the slit 1100.

At the time of observing the position 1220 for measurement, theobservation light source 1084 emits observation light toward the slit1100 under control of the controller 1023.

The emitted observation light passes through the slit 1100, and isimaged by the light receiving lens 1060.

The slit 1100 is disposed at a position optically conjugate with theposition 1220 for measurement. When the observation light source 1084emits observation light, the slit 1100 is imaged on the surface of thesample. The position where the slit 1100 is imaged corresponds to theposition 1220 for measurement. The operator can observe the position1220 for measurement by visually recognizing the image of the slit 1100through the finder hole 1340 on the integrating sphere 1041.

The optical conjugation of the slit 1100 and the position 1220 formeasurement contributes to preventing the shift of the position wherethe slit 1100 is imaged even when the position where the observationlight source 1084 is disposed is shifted. The insertion of theobservation light source 1084 into the measurement optical path 1120 byusing the insertion/extraction mechanism 1085 enables the observationlight source 1084 to be disposed near the slit 1100, and contributes toincreasing observation light that can be used as pointer light.

According to the spectrophotometer 1000 of the first embodiment,observation light that can be used as pointer light can be applied tothe position 1220 for measurement without providing large space, forexample, between the slit 1100 and the grating 1082 in thespectrophotometer 1000, and the position 1220 for measurement can beeasily observed. According to the spectrophotometer 1000 of the firstembodiment, an additional member such as a mirror is unnecessary.

1.4 Observation Light Source

The observation light source 1084 includes a light emitting diode (LED)that emits observation light. A thin LED is desired. A light sourceother than a light emitting diode may emit observation light. In thecase where an LED emits observation light, the spectrophotometer 1000can be downsized. In the case where an LED emits observation light, thepower consumption of the observation light source 1084 is reduced, andthe life of the observation light source 1084 is prolonged.

FIG. 4 is a schematic diagram illustrating an observation light sourcewith which the observation light source provided in thespectrophotometer of the first embodiment can be replaced.

The observation light source 1084 in FIG. 1 can be replaced with anobservation light source 1380 in FIG. 4. The observation light source1380 includes LEDs 1400, 1401, and 1402. The LEDs 1400, 1401, and 1402emit light 1420, light 1421, and light 1422, respectively. The light1420, the light 1421, and the light 1422 have different colors. ThreeLEDs including the LEDs 1400, 1401, and 1402 may be replaced with twoLEDs or four or more LEDs. At least a part of the LEDs 1400, 1401, and1402 may be replaced with a light source other than the LEDs.

When the observation light source 1084 is replaced with the observationlight source 1380, the controller 1023 and the operation unit 1024operate as a switching mechanism for switching light used as observationlight among the light 1420, the light 1421, and the light 1422. That is,the controller 1023 detects an operation, for selecting a color,performed on the operation unit 1024, and controls the LEDs 1400, 1401,and 1402 so that the observation light source 1380 emits light of acolor corresponding to the selected color. This enables selection ofcolor of observation light in accordance with the color of the surfaceof a sample, and enables easier observation of position 1220 formeasurement. The color of the sample may be temporarily measured at thetime of observing the position 1220 for measurement. The color of lightemitted from the observation light source 1380 may be determined byusing the result of the temporary measurement.

1.5 Emission of Illumination Light at Time of Observing Position forMeasurement

In the spectrophotometer 1000 for object color, a gap between theillumination optical system 1020 and a sample is often shielded fromlight by, for example, a target mask so that outside light other thanillumination light does not enter the gap. In the case where the gap isshielded from light, visually recognizing positions other than theposition 1220 for measurement is difficult only by applying observationlight to the position 1220 for measurement. It cannot thus be determinedwhich portion of the surface of the sample the position 1220 formeasurement corresponds to. The illumination light source 1040 may beused as an auxiliary light source at the time of observing the position1220 for measurement. The illumination light source 1040 may emitillumination light under control of the controller 1023 at the time ofobserving the position 1220 for measurement. This enables visuallyrecognizing positions other than the position 1220 for measurement, anddetermining which portion of the surface of the sample the position 1220for measurement corresponds to.

In the case where illumination light is emitted at the time of observingthe position 1220 for measurement, the controller 1023 and the operationunit 1024 function as adjustment mechanisms for adjusting the amount ofillumination light. That is, the controller 1023 detects an operation,for setting the amount of illumination light, performed on the operationunit 1024, and controls the illumination light source 1040 so that theillumination light source 1040 emits illumination light having a lightamount in accordance with the selected light amount.

1.6 Others

The above-described configuration for applying observation light to theposition 1220 for measurement may be adopted in a spectrophotometerother than the spectrophotometer 1000, having d/8 geometry, for objectcolor. The spectral spectrum of light that has been transmitted througha sample may be measured.

2. Second Embodiment

2.1 Main Difference Between First Embodiment and Second Embodiment

The main difference between the first embodiment and a second embodimentis that, in the first embodiment, the observation light source 1084 isinserted into the measurement optical path 1120 at the time of observingthe position 1220 for measurement, whereas, in the second embodiment, anobservation light source is always disposed on an optical path of zerothlight generated by a grating reflecting light to be measured. Theconfiguration of the spectrophotometer 1000 of the first embodiment or amodification thereof may be adopted in a spectrophotometer of the secondembodiment without preventing the adoption of the configuration thatcause the main difference.

2.2 Spectrophotometer

FIG. 5 is a schematic diagram illustrating a spectrophotometer of thesecond embodiment.

A spectrophotometer 2000 in FIG. 5 includes an illumination opticalsystem 2020, a light-receiving optical system 2021, a spectroscope 2022,a controller 2023, an operation unit 2024, and a camera 2025.

The illumination optical system 2020 includes an illumination lightsource 2040 and an integrating sphere 2041. The light-receiving opticalsystem 2021 includes a light receiving lens 2060. The spectroscope 2022includes a slit plate 2080, a lens 2081, a grating 2082, a line sensor2083, and an observation light source 2084. A slit 2100 is formed in theslit plate 2080.

2.3 Measurement of Spectral Spectrum

At the time of measuring a spectral spectrum, the illumination lightsource 2040 emits illumination light for illuminating a sample undercontrol of the controller 2023.

The emitted illumination light enters space 2160 inside the integratingsphere 2041 via an opening 2140 in the side surface of the integratingsphere 2041, and is diffused and multiply reflected by adiffusion/reflection surface 2180 surrounding the space 2160. Thiscauses illumination light to be uniformly diffused.

The illumination light, which has been uniformly diffused, is emittedfrom a measurement opening 2200 in the integrating sphere 2041,illuminates a region facing the measurement opening 2200, and isreflected from the surface of a sample at a position 2220 formeasurement. This generates light 2240 to be measured from the position2220 for measurement.

The generated light 2240 to be measured is imaged by the light receivinglens 2060. This generates imaged light 2280 to be measured.

The imaged light 2280 to be measured passes through the slit 2100. Thisgenerates light 2300 to be measured, which travels along a measurementoptical path 2120 between the slit 2100 and the grating 2082.

The light 2300 to be measured, which travels along the measurementoptical path 2120, is guided by the lens 2081, and diffracted andreflected by the grating 2082. This generates diffracted light includingminus first diffracted light 2320. The reflection generates zeroth light2321. The light 2300 to be measured, which travels along the measurementoptical path 2120, is subject to wavelength dispersion owing to thediffraction. As a result, the minus first diffracted light 2320 is lightthat has been subject to wavelength dispersion.

The generated minus first diffracted light 2320 is received by the linesensor 2083.

The line sensor 2083 outputs a signal representing a spectral spectrumcorresponding to the received minus first diffracted light 2320.

2.4 Observation of Position for Measurement

The spectrophotometer 2000 has a function of applying observation lightto the position 2220 for measurement. An operator can observe theposition 2220 for measurement by visually recognizing, for example, abright point and a bright line, which appears when observation light isapplied to the position 2220 for measurement, through a finder hole 2340on the integrating sphere 2041.

The observation light source 2084 is disposed on the optical path of thezeroth light 2321. Since the optical path of the zeroth light 2321 isoutside the measurement optical path 2120, retraction of the observationlight source 2084 at the time of measuring the spectral spectrum isunnecessary. For example, the movable observation light source 2084 anda movable mirror for reflecting observation light are unnecessary. Adriving mechanism for moving, for example, the observation light source2084 and the mirror for reflecting observation light is unnecessary.

At the time of observing the position 2220 for measurement, theobservation light source 2084 emits observation light toward the grating2082 under control of the controller 2023.

The emitted observation light is reflected by the grating 2082, passesthrough the slit 2100, and is imaged by the light receiving lens 2060.

When the observation light source 2084 emits observation light, the slit2100 is imaged on the surface of the sample. The position where the slit2100 is imaged corresponds to the position 2220 for measurement. Theoperator can observe the position 2220 for measurement by visuallyrecognizing the image of the slit 2100 through a finder hole 2340 on theintegrating sphere 2041.

In the second embodiment, unlike the first embodiment, the slit 2100does not need to be disposed at a position optically conjugate with theposition 2220 for measurement.

According to the spectrophotometer 2000 of the second embodiment,observation light can be applied to the position 2220 for measurementwithout providing large space in the spectrophotometer 2000, and theposition 2220 for measurement can be easily observed. According to thespectrophotometer 2000 of the second embodiment, an additional membersuch as a mirror is unnecessary.

In addition, according to the spectrophotometer 2000 of the secondembodiment, observation light is applied to the entire entrance pupil ofthe spectroscope 2022 even when the observation light source 2084 has asmall light emission area. In the observation light that has passedthrough the slit 2100, NA is equal to NA of the spectroscope 2022. Evenwhen the slit 2100 is not disposed at a position optically conjugatewith the position 2220 for measurement, the entire region formeasurement can be observed.

2.5 Wavelength of Observation Light

Observation light may have a wavelength outside the wavelength range ofa spectral spectrum to be measured. For example, in the case where thewavelength range of a spectral spectrum to be measured is in a visiblerange, observation light may have a wavelength belonging to theultraviolet region or infrared region. This prevents observation lightfrom influencing measurement of the spectral spectrum, so that theposition 2220 for measurement can be observed at the time of measuringthe spectral spectrum.

In the case where observation light has a wavelength outside thewavelength range of the spectral spectrum to be measured, the camera2025 has sensitivity to the wavelength of the observation light, andcaptures an image of the position 2220 for measurement.

2.6 Placement of Grating

FIG. 6 is a perspective view illustrating placement of a grating in thespectrophotometer of the second embodiment. FIG. 7 is a perspective viewillustrating placement of the grating compared to the placement of thegrating in the spectrophotometer of the second embodiment.

In the spectrophotometer 2000 of the second embodiment, as illustratedin FIG. 6, the grating 2082 is installed such that the minus firstdiffracted light 2320 deviates from a plane 2500. The plane 2500includes a main light beam of the light 2300, traveling along themeasurement optical path 2120, to be measured and a main light beam ofthe zeroth light 2321.

In the case where the minus first diffracted light 2320 does not deviatefrom the plane 2500 including the main light beam of the light 2300,traveling along the measurement optical path 2120, to be measured andthe main light beam of the zeroth light 2321 as illustrated in FIG. 7,the minus first diffracted light 2320 travels to the same position asthat first diffracted light 2322 travels to, and the line sensor 2083receives both the minus first diffracted light 2320 and the firstdiffracted light 2322. The minus first diffracted light 2320 isgenerated by the grating 2082 diffracting the light 2300 to be measured.The first diffracted light 2322 is generated by the grating 2082diffracting light from an optical path of the zeroth light 2321.Reflected light generated by the observation light source 2084reflecting the zeroth light 2321 or fluorescence emitted when theobservation light source 2084 receives the zeroth light 2321 is straylight, influencing the measurement of a spectral spectrum.

In contrast, in the case where the grating 2082 is rotated with respectto the minus first diffracted light 2320 and the zeroth light 2321 andthe minus first diffracted light 2320 deviates from the plane 2500including the main light beam of the light 2300, traveling along themeasurement optical path 2120, to be measured and the main light beam ofthe zeroth light 2321 as illustrated in FIG. 6, the minus firstdiffracted light 2320 travels to a position different from that thefirst diffracted light 2322 travels to, and the line sensor 2083receives the minus first diffracted light 2320 but does not receive thefirst diffracted light 2322. The minus first diffracted light 2320 isgenerated by the grating 2082 diffracting the light 2300 to be measured.The first diffracted light 2322 is generated by the grating 2082diffracting light from the optical path of the zeroth light 2321.Reflected light generated by the observation light source 2084reflecting the zeroth light 2321 or fluorescence emitted when theobservation light source 2084 receives the zeroth light 2321 does notinfluence the measurement of a spectral spectrum.

Although the invention has been described in detail, the abovedescription is illustrative in all aspects, and the invention is notlimited thereto. It is understood that countless variations notillustrated are conceivable without departing from the scope of theinvention.

REFERENCE SIGNS LIST

-   1000, 2000 Spectrophotometer-   1020, 2020 Illumination optical system-   1021, 2021 Light-receiving optical system-   1022, 2022 Spectroscope-   1023, 2023 Controller-   1024, 2024 Operation unit-   1060, 2060 Light receiving lens-   1080, 2080 Slit plate-   1081, 2081 Lens-   1082, 2082 Grating-   1083, 2083 Line sensor-   1084, 1380, 2084 Observation light source-   1085 Insertion/extraction mechanism-   1100, 2100 Slit-   1120, 2120 Measurement optical path-   1220, 2220 Position for measurement-   1240, 2240 Light to be measured-   1320, 2320 minus first diffracted light-   1400, 1401, 1402 LED-   2025 Camera-   2321 Zeroth light

The invention claimed is:
 1. A spectrophotometer comprising: alight-receiving optical system that images light to be measured from aposition for measurement and generates imaged light to be measured; aslit formation including a slit that is disposed at a position opticallyconjugate with the position for measurement, permitting at least aportion of the imaged light to be measured to pass, which travels alonga measurement optical path; a wavelength dispersing element thatperforms wavelength dispersion on the light to be measured, whichtravels the measurement optical path and outputs wavelength dispersedlight to be measured; a sensor that receives the wavelength dispersedlight to be measured, and outputs a signal representing a spectralspectrum; an observation light source that emits observation light at atime of observing the position for measurement; and aninsertion/extraction mechanism that inserts the observation light sourceinto the measurement optical path so that the observation light isemitted toward the slit at a time of observing the position formeasurement, and that retracts the observation light source outside themeasurement optical path at a time of measuring the spectral spectrum.2. The spectrophotometer according to claim 1, wherein the observationlight source includes a light emitting diode that emits the observationlight.
 3. The spectrophotometer according to claim 2, wherein theobservation light source includes a plurality of light sources, each ofthe plurality of light sources emitting a plurality of beams of light,the plurality of beams of light including different colors, and thespectrophotometer further comprises a controller configured to controlthe plurality of light sources so as to emit light of a colorcorresponding to a selected color.
 4. The spectrophotometer according toclaim 2, further comprising an illumination light source that emitsillumination light for illuminating a sample at a time of measuring thespectral spectrum and emits the illumination light also at a time ofobserving the position for measurement, and further comprising a lightreceiving optical system that receives the light from the sample that isilluminated by the illumination light source.
 5. The spectrophotometeraccording to claim 1, wherein the observation light source includes aplurality of light sources, each of the plurality of light sourcesemitting a plurality of beams of light, the plurality of beams of lightincluding different colors, and the spectrophotometer further comprisesa controller configured to control the plurality of light sources so asto emit light of a color corresponding to a selected color.
 6. Thespectrophotometer according to claim 1, further comprising anillumination light source that emits illumination light for illuminatinga sample at a time of measuring the spectral spectrum and emits theillumination light also at a time of observing the position formeasurement, and further comprising a light receiving optical systemthat receives the light from the sample that is illuminated by theillumination light source.
 7. The spectrophotometer according to claim6, further comprising a controller configured to control an amount ofthe illumination light at a time of observing the position formeasurement.